* These findings are very preliminary, but they support a decades-old (and unfortunately named) idea called the hygiene hypothesis. In order to develop properly, the hypothesis holds — to avoid the hyper-reactive tendencies that underlie autoimmune and allergic disease — the immune system needs a certain type of stimulation early in life. It needs an education.

Sometimes only minutes after the gunshots end, a computer system takes a victim’s name and displays any arrests and gang ties — as well as whether the victim has a rating on the department’s list of people most likely to shoot someone or be shot.

Police officials say most shootings involve a relatively small group of people with the worst ratings on the list. The police and social service workers have been going to some of their homes to warn that the authorities are watching them and offer job training and educational assistance as a way out of gangs.

Of the 64 people shot over the weekend, 50 of them, or 78 percent, are included on the department’s list. At least seven of the people shot over the weekend have been shot before.